The overall goal of this research proposal is to determine the functional significance of the changes in the intermediate filament (IF) cytoskeletal system that accompany the epithelial-mesenchymal transition (EMT). The EMT takes place when normal oral epithelial cells become malignant and metastasize. The EMT involves both changes in cell shape and motility. Specifically, it has been shown that one of the hallmarks of the conversion of normal epithelial cells into metastatic cells is the aberrant expression of vimentin, a Type III IF protein. These cells normally express only IF Types I and II, the keratins. We propose to carry out studies aimed at shedding new light on the functional significance of the induction of vimentin IF expression in the conversion of the normal cuboidal shape of oral epithelial cells into a mesenchymal morphology. In addition, we will attempt to determine whether vimentin expression plays a role in the increased locomotory activity of metastatic epithelial cells. The specific aims include: 1) determining the role of vimentin IF expression in the conversion of oral epithelial cells into mesenchymal cells using a variety of microscopic and molecular methodologies; 2) determining whether vimentin IF expression adds a new dimension to the cytoskeletal "crosstalk" in oral epithelial cells; 3) determining the role of plectin in establishing the molecular cross talk between IF and microtubules induced by vimentin expression in oral epithelial cells; 4) a continuation of our studies on the dynamic properties of keratin IF/tonofibrils in normal oral epithelial cells, with emphasis on alterations in their properties upon the introduction of vimentin IF.